Field of the Invention
The present application is drawn to compositions and methods for the production, purification, formulation, and use of eubacterial minicells as targeted delivery vehicles for in vivo and in vitro nucleic acid, protein, radionuclide, and small molecule drug delivery for the inhibition or prevention of disease as well as a targeted in vivo imaging and diagnostic technology.
Description of the Related Art
The following description of the background of the invention is provided to aid in understanding the invention, but is not admitted to describe or constitute prior art to the invention. The contents of the articles, patents, and patent applications, and all other documents and electronically available information mentioned or cited in this application, are hereby incorporated by reference in their entirety to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. Applicants reserve the right to physically incorporate into this application any and all materials and information from any such articles, patents, patent applications, or other documents.
The need for a robust delivery vehicle capable of encapsulation of a wide array of bioactive molecule species that is also capable of selectively targeting specific cell, organ, and tissue types is significant. Many molecular therapies are hampered by one or more in vivo limitations that include (i) adverse toxic side effects due to on-target or off-target effects on healthy cells, organs, and tissues, (ii) poor pharmacokinetics (PK) and (iii) poor uptake into cells. The targeted delivery of cytotoxic drugs, imaging agents, therapeutic nucleic acids, and other biologically active therapeutic molecules directly into the site(s) and cells that cause disease could relieve many of these deficiencies by decreasing on-target or off-target toxic effects exerted on non-disease tissue, improving the pharmacokinetics of therapeutic agents allowing for more effective administration, and enhancing uptake into cells. Accordingly, it is well recognized that the development of therapies targeted to specific cell, organ, and tissue types represents an important new frontier for clinically relevant therapeutic, diagnostic, theranostic, and imaging technologies.
In the case of chemotherapeutic agents (e.g., small molecule cytotoxic drugs) and protein toxins used in the treatment of most cancers, efficacy of the chemotherapeutic agent or protein toxin is significantly limited by toxicity to normal tissues. In addition, drug pharmacokinetic (PK) parameters contributing to systemic exposure levels frequently are not and cannot be fully optimized to simultaneously maximize anti-tumor activity and minimize side-effects, particularly when the same cellular targets or mechanisms are responsible for anti-tumor activity and normal tissue toxicity. This results in a very narrow therapeutic index, common for most cytotoxic chemotherapeutics and protein toxins.
One way to enhance the therapeutic index of existing drugs is to bind, conjugate, or package them so that a larger percentage of the administered dose ends up in the vicinity of the tumor (passive targeting) and/or inside the tumor cells (active targeting). Many different approaches to targeted delivery have been taken to date although few products are on the market. Popular approaches include the use of liposomal formulations, immunoliposomal formulations, various polymeric nanotechnologies, antibody-drug fusions/conjugates (ADC), antibody or ligand-protein toxin fusions/conjugates, and dendrimers. Liposomal formulations, including “stealth” approaches are limited because (i) they work only by passive targeting, and (ii) they are difficult to manufacture on a large scale. Immunoliposomal formulations overcome the targeting deficiencies of liposomal formulations by adding a targeting component (typically an antibody or antigen binding portion thereof). However, immunoliposomal formulations are even more difficult to manufacture than liposomal formulations, including incorporation of “stealth” technologies. Targeted polymeric nanotechnologies are limited because they require covalent linkage of the payload and targeting moiety. This complicates manufacturing, limits payload size and variety, and also exposes payload to degradation during circulation in the blood. Antibody-drug fusions/conjugates are limited mostly by payload capacity and payload metabolism. Antibody or ligand-protein toxin fusions/conjugates are also limited by off-target toxicity as well as insufficient efficacy, primarily due to the inability of the protein toxin payload to escape the endosomal compartment and effectively reach its cytosolic target following internalization by the target cell. Dendrimers have a larger payload capacity than the antibody-drug fusion/conjugates and can also bind and display targeting moieties, including antibodies. However, dendrimers are also extremely difficult to manufacture because of the complex chemistry and chemical manipulation involved in the construction process. Thus, there is a need for a delivery system to which any antibody (or other targeting moiety such as a soluble receptor ligand such as VEGF-A) can be bound or coupled in a simple non-covalent fashion, which can also encapsulate significant quantities and combinations of bioactive payloads, and is amenable to large scale manufacturing.